if (previousEntries.hasNext() && currentEntries.hasNext()) {
                        previousEntry = previousEntries.next();
                        currentEntry = currentEntries.next();
                    } else {
                        break;
                    }
                }
            }
        }

        while (currentEntries.hasNext()) {

        assertThat(it.hasNext(), is(true));
        assertThat(it.next(), is(sameClass(Integer.class)));

        assertThat(it.hasNext(), is(true));
        assertThat(it.next(), is(sameClass(Number.class)));

        assertThat(it.hasNext(), is(true));
        assertThat(it.next(), is(sameClass(Object.class)));

        assertThat(it.hasNext(), is(not(true)));
    }

    /**

         * the user calls remove().)
         */
        return iterator.hasNext() || iterable.iterator().hasNext();
      }

      @Override
      @ParametricNullness
      public T next() {
        if (!iterator.hasNext()) {
          iterator = iterable.iterator();
          if (!iterator.hasNext()) {
            throw new NoSuchElementException();
          }
        }

         * the user calls remove().)
         */
        return iterator.hasNext() || iterable.iterator().hasNext();
      }

      @Override
      @ParametricNullness
      public T next() {
        if (!iterator.hasNext()) {
          iterator = iterable.iterator();
          if (!iterator.hasNext()) {
            throw new NoSuchElementException();
          }
        }

    public SingleValueIterator(final E value) {
        this.value = value;
    }

    @Override
    public boolean hasNext() {
        return hasNext;
    }

    @Override
    public E next() {
        if (!hasNext) {
            throw new NoSuchElementException();
        }
        hasNext = false;
        return value;
    }

    @Override
    public void remove() {

        final LineIterator it = new LineIterator(reader);
        assertThat(it.hasNext(), is(true));
        assertThat(it.next(), is("aaa"));
        assertThat(it.hasNext(), is(true));
        assertThat(it.next(), is("bbb"));
        assertThat(it.hasNext(), is(true));
        assertThat(it.next(), is("ccc"));
        assertThat(it.hasNext(), is(not(true)));
    }

    /**
     * @throws Exception
     */
    @Test

        assertThat(it.hasNext(), is(true));
        assertThat(it.next(), is(sameInstance(cl3)));

        assertThat(it.hasNext(), is(true));
        assertThat(it.next(), is(sameInstance(cl2)));

        assertThat(it.hasNext(), is(true));
        assertThat(it.next(), is(sameInstance(cl1)));

        assertThat(it.hasNext(), is(not(true)));
    }

        assertThat(it.hasNext(), is(true));
        assertThat(it.next(), is("Foo"));

        assertThat(it.hasNext(), is(true));
        assertThat(it.next(), is("Bar"));

        assertThat(it.hasNext(), is(true));
        assertThat(it.next(), is("Baz"));

        assertThat(it.hasNext(), is(not(true)));
    }

    abstract T output(@ParametricNullness K key, @ParametricNullness V value);

    @Override
    public boolean hasNext() {
      return keyIterator.hasNext() || valueIterator.hasNext();
    }

    @Override
    @ParametricNullness
    public T next() {
      if (!valueIterator.hasNext()) {
        Entry<K, Collection<V>> mapEntry = keyIterator.next();
        key = mapEntry.getKey();

    abstract T output(@ParametricNullness K key, @ParametricNullness V value);

    @Override
    public boolean hasNext() {
      return keyIterator.hasNext() || valueIterator.hasNext();
    }

    @Override
    @ParametricNullness
    public T next() {
      if (!valueIterator.hasNext()) {
        Entry<K, Collection<V>> mapEntry = keyIterator.next();
        key = mapEntry.getKey();